The present invention relates to the mechanical harvesting of grapes from vines trained on a vertical trellis system.
A typical vineyard has a great number of spaced-apart vines planted in parallel rows. Some vineyards use a seven-foot spacing between vines, others use an eight-foot spacing. A typical vertical trellis system, a portion of hich is illustrated in FIG. 1, includes a vertical, wood or metal grape stake post 11 at each vine 12 throughout the vineyard, and a fruiting wire 13 attached to each post in a row, the fruiting wire being at a constant height above the ground (generally somewhere between about forty-two to forty-eight inches above the ground, depending on the vineyard), the wire being tensioned along the row to provide a support for the fruit-bearing portions of the vine, which support is substantially horizontal and continuous for the full length of the row.
Two common systems of vine training are used, a bilateral cordon system and a cane-pruned system.
In the bilateral cordon system of FIG. 1, two cordons 14 and 15, branching out from the upper end 16 of the vine trunk 17 and extending in opposite directions, are securely attached to the fruiting wire by permanent plastic ties or heavy twine. The cordons are grown along the fruiting wire so that the cordons of adjacent vines will meet. The upper ends 16 of the vine trunks will be usually anywhere from six to ten inches below the fruiting wire. The cordons are permanent wood and are not pruned back at pruning time. The laterals 18 which had grown during the growing season are pruned back to spurs at pruning time. During the growing season the bunches of grapes 19 will grow from the cordons and be closely adjacent thereto so that a relatively compact fruiting zone is formed along the horizontally supported cordons. Typically the grapes will grow in a zone extending about eight inches above and below the fruiting wire, with most of the grapes being fairly close to the level of the wire.
The trellis system also includes a foliage-supporting wire 20 positioned at the top of the posts 11 parallel to and above the fruiting wire 13. Typically the foliage wire 20 will be located about twelve to fourteen inches above the fruiting wire. During the growing season, as new laterals 18 grow from the cordons, they will first grow upwardly and attach themselves to the upper foliage wire. As they continue to grow they eventually reach a length when they are no longer strong enough to hold themselves upright. When the laterals are four to six feet long, they will droop over and form a canopy of foliage draping out away from and over the fruiting wire. When the fruit is maturing it is generally completely shaded and protected from the sun and damaging heat by the heavy foliage canopy which is hanging over it much like an umbrella. In a fully mature vine, the relatively strong laterals 18 form an open area 21 (FIG. 2) underneath the canopy and around the fruiting zone, much like the open area under a weeping willow tree.
In a cane-pruned system, illustrated in FIG. 3, the vine is pruned back each year to four to five of the one-year canes 25 (ie., those of the previous growing season) growing from the head 26 of the vine trunk 27. These one-year canes are then extended along the fruiting wire 13 and are secured thereto by semi-permanent twist ties.
Again, during the growing season the bunches of grapes 19 will grow from the one-year canes 25 and be borne in a compact fruiting zone closely adjacent the horizontally supported canes. Also, as before, new canes 28 will grow from vine head 26 and canes 25 to form a canopy over the fruiting zone. FIG. 3 also illustrates a commonly used trellis system wherein a crossarm 29 is secured to the top of each post 11 to support two foliage wires 20 and 20a. The crossarms and two foliage wires serve to widen out the canopy since the vine laterals 28 are supported further away from the center of the vine in a direction transverse to the centerline of the row. The open area 21 under the canopy (FIG. 4) is, of course, correspondingly widened.
A cordon-trained vine can also be trained on the T-trellis system of FIG. 3, and a cane-pruned vine can also be trained on the single foliage wire trellis system of FIG. 1 if desired.
The most widely used method for the harvesting of grapes from the vine and trellis system of FIGS. 1-4 utilize opposed horizontal striker rods on each side of the row which are pivoted about vertical axes located on either side of the vine canopy. The rods are oscillated about these axes so that they penetrate the vine canopies and strike against the fruit to remove it.
Although this method has proven effective in the removal of grapes from the vines, it does have a disadvantage in that oftentimes damage is done to the vine and fruit during the harvesting process.
In addition to providing shade to the grapes, the leaves of the vine canopy act as small nutrient factories, taking the light from the sun and converting it to nutrients to supply the vine with energy to grow the crop. During the course of the growing season, almost all of the nutrients supplied by the leaves are used to produce the heavy crop of grapes on the vine. After harvest, the leaves are still essential to supply nutrients for the building up of carbohydrates in the vine to help produce the next year's crop. It has been found that if all of the canopy leaves are removed at harvest time for several successive years, the strength of the vine is reduced to a point wherein there is a substantial crop reduction.
Although the pivotal striker system has been developed so that it does not remove all of the leaves at harvest time, it does beat off enough of the leaves so that there is considerable concern in the vineyard industry of a possible crop reduction in the future. In some cases, crop reductions have actually been experienced.
An additional disadvantage of the pivot striker system is that the leaves which are beaten off the vines are often shattered into small particles which when mixed with the harvested fruit are very difficult to remove. These small particles travel with the fruit to the winery and when the fruit is crushed they are fermented with the crushed fruit into wine. The fermented leaf particles form an aldehyde during fermentation which imparts a bitter and objectionable taste to the wine.
Another disadvantage of this harvesting system is that the beating of the striker rods often causes damage to the cambium layer of the vine canes and in some cases breaks the spurs from the cordons. This vine damage reduces the effectiveness of those canes in carrying nutrients to the fruit. It can also cause a rotting at the point of damage and in some cases will cause the canes to actually die.
In an effort to reduce the vine damage and leaf-removal problems of the pivotal striker method, attempts have been made to harvest grapes by gripping the trunk of the vine at the upper end thereof and by then shaking the trunk back and forth transversely of the row. The violent shaking of the trunk transfers an energy up through the trunk of the vine and down the cordon or canes when the grapes are attached so that the grapes will be shaken off.
Although the trunk-shaker method does eliminate the leaf-removal, it has not proven to be a very efficient method of removing the fruit. Also, even though the particular vine damages caused by the pivotal striker system are avoided, different forms of damage to the vine and trellis system are done by the trunk-shaker method.
One disadvantage of this method is that not all vines are strong enough or stiff enough to transmit the necessary energy from the trunk to where the fruit is positioned. In a cordon-pruned vine where the cordons are young and flexible, or in a cane-pruned vine wherein the fruit is borne by one-year canes, the fruit is not removed out at the ends of the cordons or canes because the shaking energy is simply not transmitted that far with enough force to remove the fruit.
Even with more mature cordons, the trunk-shaking method does not work effectively with hard-to-pick varieties of grapes. Generally, on a hard-to-pick variety, fruit is removed fairly effectively up to approximately two feet from the head of the vine or post. Beyond that distance, there is poor removal of fruit.
In addition to having a relatively low harvesting efficiency, the trunk-shaking method does cause damage. Sometimes the energy imparted to the trunk of a cordon-trained vine will actually split the trunk vertically down from the point where the cordons branch off all the way to the ground, killing the vine. Also, since the energy applied at the trunk must be applied with enough amplitude to shake the fruit from the vine, such applied energy has in many instances been strong enough to break trellis stakes right at the ground.
It is the principal object of the present invention to provide a harvesting method which has a high efficiency of fruit-removal, which minimizes leaf-removal from the vine canopy and which minimizes vine and trellis damage.